Efficient extracellular expression of a foreign protein in smptomyos using secretory protease inhibitor (SSI) gene fusions

Using the gene for a secreted protease inhibitor, Streptomyces subtilisin inhibitor (SSI), we have established a secretory expression system for the products of foreign genes in Streptomyces. A sex pheromone peptide, cADl, of Enterococcus fae- calis was expressed and secreted as a stable complete fusion protein with SSI in amounts comparable to the native SSI in S. lividans 66. Recombinant cADl, isolated from the fusion protein by chemical digestion with BrCN, has the same amino acid composition and sequence, retention time on reverse phase HPLC, molecular mass, and biological activity as authentic cADl. This system should be useful for the efficient expression of other foreign gene products, and as a model for heterologous gene expression in Streptomyces.